If a 2-ounce skin cream contains 200,000 I.U. of Vitamin A, what percentage would that be ?

Answer: There's not really an accurate answer you could get (aside from calling the company to see if they roll a percentage), primarily because IU is a measurement of potency, not counterweight or volume (which creams are measured in, resembling Ounces).
One thing I can articulate is that if the 2 ounce container has 200,000 IU, that funds that every 1/8th teaspoon (which is a typical dose for many creams) would simply have nearly 2,000 IU, which is about 40% of the RDA (which is the recommended on a daily basis minimum for basic health), and with the sole purpose 20% of the normal dose of Vitamin A. That's a pretty low amount unless you're taking a multivitamin as very well or have a upright source of Vitamin A in your diet.